Bobbinless coil and method of manufacturing the same

ABSTRACT

A pair of disk-shaped guide members abut on opposite end surfaces in the axial direction of a conductor wire wound round into a coil shape by using a separable jig. The guide members are biased toward each other by engaging a part of the conductor wire with engaging portions formed at circumferences of the pair of guide members. Then, the jig is separated from the center of the conductor wire, thereby maintaining the coiled shape of the conductor wire to create a bobbinless coil having an exposed inner peripheral surface. In addition, the pair of disk-shaped guide members are biased toward each other by utilizing a part of the conductor wire, and therefore a special biasing member is not needed.

RELATED APPLICATION DATA

Japanese priority application No. 2005-8554, upon which the presentapplication is based, is hereby incorporated in its entirety herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bobbinless coil comprising aconductor wire which is wound into a coil shape and which exposes itsinner peripheral surface, and a method of manufacturing the bobbinlesscoil.

2. Description of the Related Art

A coil used for an electromagnetic actuator or a motor is wound aroundan insulator which is generally called a bobbin. However, a bobbinlesscoil without such a bobbin is known from Japanese Patent ApplicationLaid-open No. 10-172823. In this bobbinless coil, a tape having abonding layer is spirally wound around a conductor wire; the conductorwire is wound into a cylindrical shape to form a coil body; a pluralityof spots in a circumferential direction of the coil body are fixed tomaintain the shape of the bobbinless coil.

However, the above described bobbinless coil has a problem that theshape of the coil body is likely to be inaccurate because the bobbinwhich becomes a guide does not exist when winding the conductor wire.Further, because the conductor wire is bonded over the entire length,there is not only a problem of requiring a large amount of tape with abonding layer, but also a problem of requiring a large number of stepsfor winding the tape with the bonding layer.

SUMMARY OF THE INVENTION

The present invention is made in view of the above describedcircumstances, and has an object to keep a wound conductor wire of abobbinless coil in a coil shape with a simple structure.

In order to achieve the above object, according to a first feature ofthe present invention there is provided a bobbinless coil comprising: aconductor wire wound into a coil shape and having an exposed innerperipheral surface; a pair of disk-shaped guide members abutting onopposite end surfaces of the coiled conductor wire in a direction of anaxis thereof; and a biasing member biasing the pair of guide memberstoward each other.

The first and the second guide members 65 and 66 of the embodimentcorrespond to the guide members of the present invention.

With the arrangement of the first feature, a pair of disk-shaped guidemembers abut on opposite end surfaces in a direction of an axis of thecoiled conductor wire, and the pair of guide members are biased by abiasing member in a direction to be close to each other. Therefore, itis possible to maintain the shape of the bobbinless coil which is woundround into the coil shape and which has an exposed inner peripheralsurface.

According to a second feature of the present invention, in addition tothe first feature, the biasing member is a part of the conductor engagedwith engaging parts which are formed at circumferences of the pair ofdisk-shaped guide members.

With arrangement of the second feature, the biasing member is utilizedas a part of the conductor wire, and the part of the conductor wire isengaged with engaging parts which are formed at circumferences of thepair of disk-shaped guide members, whereby the pair of guide members canbe biased in the direction to be close to each other without using aspecial biasing member.

According to a third feature of the present invention, there is provideda method of manufacturing the bobbinless coil according to the first orsecond feature, comprising the steps of: winding the conductor wire intothe coil shape around an outer periphery of a bobbin jig which extendscentrally through the pair of disk-shaped guide members and is guidedthereby; biasing the pair of guide members toward each other by engagingat least one end of the conductor wire with outer peripheral portions ofthe pair of guide members and pulling the one end of the conductor wirein the direction of the axis; and separating the bobbin jig from theconductor wire which is wound round into the coil shape and the pair ofguide members.

With the arrangement of the third feature, the conductor wire is woundinto the coil shape around an outer periphery of a bobbin jig whichextends centrally through the pair of disk-shaped guide members and isguided thereby; the pair of guide members are biased toward each otherby engaging at least one end of the conductor wire with outer peripheralportions of the pair of guide members and pulling the one end of theconductor wire in the direction of the axis; and then the bobbin jig isseparated from the conductor wire which is wound round into the coilshape and the pair of guide members. Therefore, it is possible tomanufacture a bobbinless coil which accurately maintains its coil shapewithout the use of tape as in the coil of Japanese Patent ApplicationLaid-open No. 10-172823 or other bonding material. In other words, it ispossible to construct the bobbinless coil of only the conductor wire andthe guide members.

The above-mentioned object, other objects, characteristics, andadvantages of the present invention will become apparent from anexplanation of an exemplary embodiment, which will be described indetail below with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 7 show one embodiment of the present invention.

FIG. 1 is a vertical sectional view of an active vibration isolationsupport system.

FIG. 2 is an enlarged view of Part 2 in FIG. 1.

FIG. 3 is a view showing a state in which a conductor wire is woundaround a bobbin jig.

FIG. 4 is a plane view of a coil assembly.

FIG. 5 is a view taken from the direction of an arrow 5 in FIG. 4.

FIG. 6 is a sectional view taken along a line 6-6 in FIG. 4.

FIG. 7 is a flowchart explaining the operation of the system.

DESCRIPTION OF THE PRESENT EMBODIMENT

The present invention will be described based on an embodiment of thepresent invention shown in the attached drawings.

Embodiment 1

As shown in FIGS. 1 and 2, an active vibration isolation support systemM (active control mount) for elastically supporting an engine of anautomobile on a vehicle body frame, has a substantially symmetricalstructure with respect to an axis L. Between a flange part 11 a at alower end of a substantially cylindrical upper housing 11 and a flangepart 12 a at an upper end of a substantially cylindrical lower housing12, a flange part 13 a at an outer periphery of a substantiallycup-shaped actuator case 13 with a top open surface, an outer peripheralportion of an annular first elastic body support ring 14, and an outerperipheral portion of an annular second elastic body support ring 15 areoverlaid on one another and connected by crimping. At this time, anannular first floating rubber 16 is interposed between the flange part12 a of the lower housing 12 and the flange part 13 a of the actuatorcase 13, and an annular second floating rubber 17 is interposed betweenan upper portion of the actuator case 13 and an inner surface of thesecond elastic body support member 15, whereby the actuator case 13 isfloatingly supported to be relatively movable with respect to the upperhousing 11 and the lower housing 12.

A lower end and an upper end of a first elastic body 19 formed of thickrubber are respectively joined to the first elastic body support ring 14and a first elastic body support boss 18 which is disposed on the axis Lby vulcanization bonding. A diaphragm support boss 20 is fixed to a topsurface of the first elastic body support boss 18 with a bolt 21, and anouter peripheral portion of a diaphragm 22 whose inner peripheralportion is joined to the diaphragm support boss 20 by vulcanizationbonding is joined to the upper housing 11 by vulcanization bonding. Anengine mounting part 20 a which is integrally formed on a top surface ofthe diaphragm support boss 20 is fixed to an engine not shown. A vehiclebody mounting part 12 b at a lower end of the lower housing 12 is fixedto a vehicle body frame not shown.

A flange part 23 a at a lower end of a stopper member 23 is connected toa flange part 11 b at an upper end of the upper housing 11 with bolts 24and nuts 25. The engine mounting part 20 a projectingly provided on thetop surface of the diaphragm support boss 20 faces a stop rubber 26which is mounted to an inner surface of an upper portion of the stoppermember 23 so that the engine mounting part 20 a can abut on the stoprubber 26. When a large load is inputted into the active vibrationisolation support system M, the engine mounting part 20 a abuts on thestopper rubber 26, whereby excessive displacement of the engine issuppressed.

An outer peripheral portion of a second elastic body 27 formed of rubberin a film form is joined to the second elastic body support ring 15 byvulcanization bonding. A movable member 28 is joined to a centralportion of the second elastic body 27 by vulcanization bonding so as tobe embedded in the central portion. A disk-shaped partition wall member29 is fixed between the top surface of the second elastic body supportring 15 and an outer peripheral portion of the first elastic body 19. Afirst liquid chamber 30 defined by the partition wall member 29 and thefirst elastic body 19 as well as a second liquid chamber 31 defined bythe partition wall member 29 and the second elastic body 27 communicatewith each other via a communication hole 29 a formed in a centralportion of the partition wall member 29.

An annular communication passage 32 is formed between the first elasticbody support ring 14 and the upper housing 11. One end of thecommunication passage 32 communicates with the first liquid chamber 30via a communication hole 33, and the other end of the communicationpassage 32 communicates with a third liquid chamber 35 which is definedby the first elastic body 19 and the diaphragm 22 via a communicationhole 34.

Next, the structure of an actuator 41 for driving the movable member 28will be described.

A fixed core 42, a coil assembly 43 and a yoke 44 are mounted inside theactuator case 13 sequentially from the lower side to the upper side. Thecoil assembly 43 comprises a bobbinless coil 46 disposed between thefixed core 42 and the yoke 44, and a coil cover 47 which covers an outerperiphery of the bobbinless coil 46. A connector 48 is integrally formedat the coil cover 47 so as to penetrate through openings 13 b and 12 cformed in the actuator case 13 and the lower housing 12 and extend tothe outside.

Here, a method of manufacturing the coil assembly 43 will be described.

As shown in FIG. 3, a bobbin jig 62 for winding a conductor wire 61 intoa coil shape comprises a jig body 63 and a holding member 64. The jigbody 63 includes a disk-shaped flange part 63 a and a columnar windingpart 63 b, and a female screw 64 a of the holding member 64 is screwedonto a male screw 63 c provided at a tip end of the winding part 63 b. Afirst guide member 65 of a synthetic resin is fitted on the flange part63 a of the jig body 63, and comprises a disk-shaped plate which isperpendicular to the axis L. A second guide member 66 of a syntheticresin also comprises a disk-shaped plate which is perpendicular to theaxis L the same as the first guide member 65. The second guide member 66is positioned by the holding member 64 with the female screw 64 ascrewed onto the male screw 63 c of the jig body 63 in a state in whichthe second guide member 66 is fitted to a step portion provided at anouter periphery of the winding part 63 b of the jig body 63.

As described above, in the state in which the first and second guidemembers 65 and 66 are held at the bobbin jig 62, the conductor wire 61is wound using, as the guide, the outer peripheral surface of thewinding part 63 b of the jig body 63 as well as opposed surfaces betweenthe first and second guide members 65 and 66.

As is obvious from FIGS. 4 to 6, four engaging parts 65 c are formed at90° intervals at an outer peripheral portion of the first guide member65. Four engaging parts 66 c are formed at 90° intervals at an outerperipheral portion of the second guide member 66, and between twoengaging parts 66 c and 66 c among them, a start end projection 66 d anda terminal end projection 66 e are formed. A start end (winding startside) of the conductor wire 61 is first wound around the start endprojection 66 d of the second guide member 66, from which the conductorwire 61 is guided radially inward to the winding part 63 b to be woundaround the winding part 63 b.

A terminal end of the conductor wire 61 is wound into a coil shape fromradially inside to outside using the winding part 63 b and the first andthe second guide members 65 and 66 as the guide, and is wound in acircumferential direction to be alternately engaged with the fourengaging parts 65 c of the first guide member 65 and the four engagingparts 66 c of the second guide member 66. By giving a predeterminedtensile force to the conductor wire 61 in this process, the first andsecond guide members 65 and 66 are biased in the direction to be closeto each other. Thus, a part of the conductor wire engaged with andconnected to the engaging parts 65 c, 66 c with the predeterminedtensile force functions as a biasing member for the bobbinless coil. Theterminal end (winding end) of the conductor wire 61 is wound around theterminal end projection 66 e of the second guide member 66.

A load acting on an inner diameter portion of the conductor wire 61which is wound into the coil shape is determined by a diameter of thewinding part 63 b around which the conductor wire 61 is wound, a wirediameter of the conductor wire 61, the number of windings and thewinding tensile force of the conductor wire 61. For example, in the casewhere the conductor wire 61 is wound with the same winding tensileforce, the load acting on the inner diameter portion becomes larger asthe number of windings becomes larger, and a plastic deformation zone ofthe conductor wire 61 becomes large. Accordingly, the plasticdeformation zone of the conductor wire 61 can be controlled by adjustingthe diameter of the winding part 63 b around which the conductor wire 61is wound, the wire diameter of the conductor wire 61, and the number ofwindings and the winding tensile force of the conductor wire 61.

However, because the diameter of the winding part 63b, the wire diameterof the conductor wire 61, and the number of windings of the conductorwire 61 affect the performance of the bobbinless coil 46, in thisembodiment, the conductor wire 61 at that portion is plasticallydeformed by enhancing the winding tensile force of three layers ofconductor wire 61 which is densely shown in FIG. 3, to thereby enhancethe holding function of the coil shape.

When the coil shape of the wound conductor wire 61 is maintained in thismanner, the holding member 64 is separated from the jig body 63, and thejig body 63 is extracted from the inner peripheral surface of theconductor wire 61. The synthetic resin coil cover 47 is molded on theouter peripheral surface excluding the inner peripheral surface of thecoil-shaped conductor wire 61, and on outer surfaces of the first andthe second guide members 65 and 66, to thereby complete the coilassembly 43. When the coil cover 47 is molded, the connector 48 isintegrally formed therein.

Returning to FIGS. 1 and 2, a seal member 49 is disposed between the topsurface of the coil cover 47 and the undersurface of the yoke 44, and aseal member 50 is disposed between the undersurface of the bobbinlesscoil 46 and the top surface of the fixed core 42. These seal members 49and 50 prevent water and dust from entering an inner space of theactuator 41 from the openings 13 b and 12 c formed in the actuator case13 and the lower housing 12.

A bearing member 51 having a thin-walled cylindrical shape is verticallyslidably fitted to an inner peripheral surface of a cylindrical part 44a of the yoke 44. An upper flange 51 a folded radially inward is formedat an upper end of the bearing member 51, and a lower flange 51 b foldedradially outward is formed at a lower end. A set spring 52 is disposedunder compression between the lower flange 51 b and a lower end of thecylindrical part 44 a of the yoke 44. The lower flange 51 b is pressedby a resilient force of the set spring 52 against a top surface of thefixed core 42 via an elastic body 53, so that the bearing member 51 issupported by the yoke 44.

A substantially cylindrical movable core 54 is vertically slidablyfitted onto an inner peripheral surface of the bearing member 51. A rod55 extending downward from a center of the movable member 28 looselypenetrates through a center of the movable core 54, and a nut 56 isfastened to a lower end of the rod 55. A set spring 58 is disposed undercompression between a spring seat 57 provided on a top surface of themovable core 54 and an undersurface of the movable member 28, and themovable core 54 is pressed by a resilient force of the set spring 58against the nut 56 to be fixed. In this state, an undersurface of themovable core 54 and the top surface of the fixed core 42 are opposed toeach other with a conical air gap g therebetween. The rod 55 and the nut56 are loosely fitted in an opening 42 a formed in a center of the fixedcore 42, and the opening 42 a is closed by a plug 60 via a seal member59.

An electronic control unit U, to which a crank pulse sensor Sa fordetecting a crank pulse outputted with rotation of a crankshaft of anengine is connected, controls energization to the actuator 41 of theactive vibration isolation support system M. The crank pulses of theengine are outputted 24 times per rotation of the crankshaft, namely,one crank pulse is outputted at each 15° of the crank angle.

Next, the operation of the embodiment of the present invention with theabove described structure will be described.

When engine shake vibration at low frequency occurs during traveling ofan automobile, and the first elastic body 19 is deformed by the loadinputted from the engine via the diaphragm support boss 20 and the firstelastic body support boss 18, the capacity of the first liquid chamber30 changes, so that liquid comes and goes between the first liquidchamber 30 and the third liquid chamber 35 which are connected via thecommunication passage 32. When the capacity of the first liquid chamber30 increases/decreases, correspondingly the capacity of the third liquidchamber 35 decreases/increases, but the capacity change of the thirdliquid chamber 35 is absorbed by the elastic deformation of thediaphragm 22. In this case, the shape and size of the communicationpassage 32 and the spring constant of the first elastic body 19 are setto exhibit a low spring constant and a high damping force in thefrequency region of the engine shape vibration, thereby effectivelyreducing the vibration transmitted from the engine to the vehicle frame.

The actuator 41 is kept in the non-operational state in the frequencyregion of the engine shake vibration.

When vibration at a frequency higher than that of the engine shakevibration, namely, vibration during idling due to rotation of thecrankshaft of the engine, or vibration when traveling with cylinders ina cut-off state is generated, the liquid inside the communicationpassage 32 which connects the first liquid chamber 30 and the thirdliquid chamber 35 enters a stuck state, and cannot exhibit a vibrationisolating function, and therefore the actuator 41 is driven to exhibitthe vibration isolating function.

The electronic control unit U controls energization to the bobbinlesscoil 46 based on the signal from the crank pulse sensor Sa in order toexhibit the vibration isolating function by operating the actuator 41 ofthe active vibration isolation support system M.

Namely, in the flowchart in FIG. 7, the electronic control unit U firstreads the crank pulse which is outputted every 15° of the crank anglefrom the crank pulse sensor Sa in Step S1, and calculates the timeinterval of the crank pulses by comparing the read crank pulse withcrank pulse which is the reference (TDC signal of a specific cylinder)in Step S2. In Step S3, the electronic control unit U calculates a crankangular speed ω by dividing the crank angle of 15° by the time intervalof the crank pulses. In Step S4, the electronic control unit Ucalculates a crank angular acceleration dω/dt by differentiating thecrank angular speed ω with time. In Step S5, the electronic control unitU calculates torque Tq about the crankshaft of the engine according toTq=I×dω/dtwhere moment of inertia about the crankshaft of the engine is I. Thetorque Tq is 0 when it is assumed that the crankshaft rotates at aconstant angular speed ω, but in the expansion stroke, the angular speedω increases due to acceleration of the piston, and in the compressionstroke, the angular speed ω decreases due to deceleration of the pistonto cause the crank angular acceleration dω/dt. Therefore, the torque Tqproportional to the crank angular acceleration dω/dt occurs.

In Step S6, the electronic control unit U determines the maximum valueand the minimum value of the torques adjacent timewise. In Step S7, theelectronic control unit U calculates a difference between the maximumvalue and the minimum value of torque, namely, an amplitude at theposition of the active vibration isolation support system M whichsupports the engine. In step S8, the electronic control unit Udetermines a duty waveform and timing (phase) of an electric currentwhich is applied to the bobbinless coil 46 of the actuator 41.

Thus, when the engine moves downward with respect to the vehicle bodyframe and the first elastic body 19 deforms downward to decrease thecapacity of the first liquid chamber 30, the bobbinless coil 46 of theactuator 41 is excited in this timing, so that the movable core 54 movesdownward toward the fixed core 42 by the attraction force generated inthe air gap g and the second elastic body 27 deforms downward by beingpulled by the movable member 28 connected to the movable core 54 via therod 55. As a result, the capacity of the second liquid chamber 31increases, and therefore the liquid in the first liquid chamber 30,which is compressed by the load from the engine, passes through thecommunication hole 29 a of the partition wall member 29 and flows intothe second liquid chamber 31, thus reducing the load transmitted fromthe engine to the vehicle body frame.

When the engine subsequently moves upward with respect to the vehiclebody frame, and the first elastic body 19 deforms upward to increase thecapacity of the first liquid chamber 30, the bobbinless coil 46 of theactuator 41 is demagnetized in this timing, so that the attraction forcegenerated in the air gap g disappears and the movable core 54 can freelymove. Therefore, the second elastic body 27 which has been deformeddownward restores upward with its own elastic restoring force. As aresult, the capacity of the second liquid chamber 31 decreases, andtherefore, the liquid in the second liquid chamber 31 passes through thecommunication hole 29 a of the partition wall member 29 and flows intothe first liquid chamber 30, thus allowing the engine to move upwardwith respect to the vehicle body frame.

By magnetizing and demagnetizing the bobbinless coil 46 of the actuator41 in accordance with the vibration cycle of the engine as describedabove, it is possible to generate an active vibration control forcewhich prevents the vibration of the engine from being transmitted to thevehicle body frame.

Thus, the first and the second guide members 65 and 66 are caused toabut on opposite end surfaces in the direction of the axis L of theconductor wire 61 wound round into the coil shape, and the pair of guidemembers 65 and 66 are biased in the direction to be close to each otherby utilizing the conductor wire 61. Therefore, it is possible toreliably maintain the shape of the bobbinless coil 46 having theconductor wire 61 which is wound round into the coil shape and whichexposes its inner peripheral surface, and eliminate the need of thespecial biasing member to reduce the number of the components. Further,it is possible to prevent loosening of the conductor wire 61, whilereducing the number of components and the cost by removing the bobbinand the tape having a bonding layer from the bobbinless coil 46.Furthermore, it is possible to reduce the inner diameter of thebobbinless coil 46 corresponding to the amount of the bobbin, thusreducing the resistance and inductance to enhance electric currentresponsiveness.

The exemplary embodiment of the present invention has been describedabove, but various changes in design can be made without departing fromthe subject matter of the present invention.

For example, the bobbinless coil 46 of the active vibration isolationsupport system M is shown as an example of the embodiment, but thebobbinless coil of the present invention is applicable to any other useand purpose.

Also, in the exemplary embodiment, the first and the second guidemembers 65 and 66, which are disposed at opposite ends in the axis Ldirection of the conductor wire 61 wound round into the coil shape, arebiased by the conductor wire 61 itself, but they can be biased by usingany biasing member (a wire or a spring) instead of the conductor wire61.

In the exemplary embodiment, the first and second guide members 65 and66 are biased at one end of the conductor wire 61, but they may bebiased at opposite ends of the conductor wire 61.

The method of winding the conductor wire 61 for biasing the first andsecond guide members 65 and 66 in the direction to be close to eachother is optional.

1. A bobbinless coil comprising: a conductor wire wound into a coilshape and having an exposed inner peripheral surface; a pair ofdisk-shaped guide members abutting on opposite end surfaces of thecoiled conductor wire in a direction of an axis L thereof; and a biasingmember biasing the pair of guide members toward each other; wherein thebiasing member is a part of the conductor wire engaged with engagingparts which are formed at circumferences of the pair of disk-shapedguide members, thereby connecting the disk-shaped guide members to theconductor wire wound into the coil shape.
 2. The bobbinless coilaccording to claim 1, wherein the part of the conductor wire is pulledin an axial direction of the coil when it is engaged with the engagingparts so that the part of the conductor wire remains engaged with theengaging parts under a predetermined tensile force.
 3. The bobbinlesscoil according to claim 1, wherein the part of the conductor wire is anend part.
 4. The bobbinless coil according to claim 1, wherein the partof the conductor wire is a terminal end part.
 5. A bobbinless coilcomprising: a conductor wire wound into a coil shape and having anexposed inner peripheral surface: a pair of disk-shaped guide membersabutting on opposite end surfaces of the coiled conductor wire in adirection of an axis L thereof; and a biasing member biasing the pair ofguide members toward each other; wherein start and terminal endprojections are provided with the guide members, and start and terminalends of the conductor wire are engaged with the start and terminal endprojections, respectively.
 6. The bobbinless coil according to claim 1,wherein the disk-shaped guide members are planar, and the engaging partsof the guide members are disposed radially outwardly of the conductorwire wound into the coil shape.
 7. The bobbinless coil according toclaim 1, wherein each of the disk-shaped guide members includes at leasttwo of said engaging parts spaced from each other at the circumferenceof the guide member.
 8. A bobbinless coil comprising: a conductor wirewound into a coil shape and having an exposed inner peripheral surface;a pair of disk-shaped guide members abutting on opposite end surfaces ofthe coiled conductor wire in a direction of an axis L thereof; and abiasing member biasing the pair of guide members toward each other;wherein start and terminal ends of the conductor wire are connected toat least one of the disk-shaped guide members.
 9. A bobbinless coilcomprising: a conductor wire wound into a coil shape and having anexposed inner peripheral surface; a pair of disk-shaped guide membersabutting on opposite end surfaces of the coiled conductor wire in adirection of an axis L thereof; and a biasing member biasing the pair ofguide members toward each other; wherein said coil shape includesmultiple layers of the conductor wire wound in a radial direction of thecoil shape, with a radially innermost one of said layers forming saidexposed inner peripheral surface of the coil shape, and said biasingmember being disposed outwardly of a radially outermost one of saidlayers.
 10. A bobbinless coil comprising: a conductor wire wound into acoil shape and having an exposed inner peripheral surface; a pair ofdisk-shaped guide members abutting on opposite end surfaces of thecoiled conductor wire in a direction of an axis L thereof; and a biasingmember biasing the pair of guide members toward each other; wherein someof said multiple layers of the conductor wire closest to said exposedinner peripheral surface of the coil shape are wound with a greaterwinding tensile force than others of said multiple layers.
 11. Abobbinless coil consisting of: a conductor wire wound into a coil shapeand having an exposed inner peripheral surface; a pair of disk-shapedguide members abutting on opposite end surfaces of the coiled conductorwire in a direction of an axis L thereof; and a biasing member biasingthe pair of guide members toward each other.